1. Field of the Invention
The invention concerns a device to fasten a casing tube switch module to the casing tube of a motor vehicle steering shaft.
2. Background Art
Casing tube switch modules are switch modules that are arranged in the area of the casing tube of a motor vehicle steering shaft. These modules carry, for example, steering column switches and similar things. Depending on the embodiment, part of the casing tube switch module can also be a contact coil cassette, an angular position sensor, or something similar.
As a rule, the casing tube switch module is arranged so that it is concentric to the casing tube of the steering shaft and is fastened to it. Such a casing tube switch module can—as provided in DE 199 42 247 C1—be fastened with a stiffening module and coupling module which is rigidly connected with the casing tube. This module includes connection elements to which the casing tube switch module can be fastened by a stable clip connection, for example. The object of this document provides that, to create the entire steering column module, first the casing tube switch module is fastened to the casing tube and then the steering wheel is mounted onto the end of the steering shaft that reaches through the casing tube switch module.
In other embodiments, the casing tube switch module is held to the casing tube by pipe clamps or means of axial attachment.
DE 199 42 818 A1 discloses another casing tube switch module which, in contrast to the previously described prior art, is fastened not to the casing tube but rather to the steering wheel. This casing tube switch module is rotationally decoupled from the steering wheel itself. To make sure there is no twisting, the casing tube switch module is held torsionally fixed to the casing tube, for example by putting it on a peg. An advantage of this embodiment is that no tolerances have to be compensated at the interface of the steering wheel and the casing tube switch module. The consequence of this is that a motion gap between the steering wheel and the casing tube switch module is regularly equal, independent of the tolerances that arise. Another advantage of the object of this document is that the casing tube switch module does not require additional measures to mount it on the casing tube.
However, it has turned out that it is preferable to use casing tube switch modules which are fastened directly to the casing tube. Nevertheless, it is also desired to fasten such a casing tube switch module to the casing tube without additional measures when the steering wheel is put on or fastened to the steering shaft.